Suspension insulators provided with a core and an envelope



Jan. 29, 1963 .1. Moussou 3,076,053

SUSPENSION INSULATORS PROVIDED WITH A CORE AND AN ENVELOPE Filed Feb. 15. 1961 United States Patent f 3,076,053 SUSPENSION INSULATORS PROVIDED WITH A CORE AND AN ENVELOPE Jean Mousson, Pouzac, France, assigner to Compagnie Generale dElectro-Ceramique, Paris, France, a company of France Filed Feb. 15, 1961, Ser. No. 89,481 Claims priority, application France Feb. 24, 1960 4 Claims. (Cl. 174-179) The present invention relates to composite insulators consisting basically of an insulating core resistant to traction and connected to two metal fittings, the core being arranged inside a protective insulating envelope made of some ceramic, for example.

The core is generally made of bonded fibres, an example being resin-bonded glass fibres.

It is the object of the invention to provide between the envelope and the core an insulating space in which it will be impossible for the electric arc to find a path easier than the path which it can find in the space outside the envelope.

To this end, in insulators proposed hitherto, it is the usual practice to fill this annular space with an oil, a compound or a resin. Such executions, however, are not entirely satisfactory since the oil calls for the provision of seals which are diticult to execute, while compounds or resins have a different coeicient of expansion from that of the envelope, which in turn results in crevices, shearings, unbondings, all of which constitute many possible paths for the arc.

In accordance with the invention, means' are used to entirely overcome these drawbacks.

The embodiments described hereunder with reference to the accompanying drawing will give a clear understanding of the means employed in and the scope of the invention. In the drawings,

FIG. 1 is a sectional view of an insulator embodying features of the present invention;

FIG. 2 is a similar view of another embodiment of the invention; and

FIG. 3 is a corresponding view of another embodiment.

Referring now to FIG. l, the insulator shown consists basically of an insulating pin 1, an insulating envelope 2, attachment fittings 3 sealed into pin 1, and a capping plate 4 tightened onto each end of the envelope by a nut 5 screwed onto the fitting 3, using an interposed seal 6 in each case. In accordance with the invention, there is interposed between the core and the envelope a set of rings 7 made of some insulating material such as a compressed gelatinized cellulose which is sold under the trademark Presspahn and each of these rings is provided with a small flange smeared with a polymerizable resin, such as a resin of the ethoxy type sold under the trademark Araldite. These rings are in the form of an insulating blade and are force fitted onto pin 1 and into envelope 2, the flanges on the rings being generously smeared with resin and carefully applied against elements 1 and 2, then subjected to polymerization treatment. There is thus formed an insulating annular space comprising a plurality of insulating gaps in series; each separation element 7 is bonded to the envelope and to the core over a narrow area only, so that stresses arising from the difference in expansion are reduced, thereby enabling bonding to be ensured between components 1, 7 and 2 without cracks or crevices resulting.

Instead of producing the annular space in the form of several layers of air each imprisoned between a pair of insulating elements 7, it is also possible, in accordance with FIG. 2, to fill the annular space 1t) with a solid insulating medium such as a compound or a resin, then to deposit on that layer a thin layer 11 of some substance such as an elastomer, `of which Thiokol-bearing rubber is an example, capable of adhering to the walls or envelope 12 and to core 13. Thiokol is a trademark for a synthetic elastomer composed of polysullides. This layer 11 is in turn covered by a further layer 10 and thereafter by yet another layer 11, and so on until all of the annular space is filled. In this way, stresses in the resin-based filler material are restricted and provision is also made to ensure that the annular space is divided up by a number of insulating diaphragms that are perfectly bonded to the envelope and to the core and arranged in series. Two plates 14 are tightened onto the envelope by means of nuts screwed onto the fittings 15.

As shown in the embodiment of FG. 3, the annular insulating space can be provided, alternatively, by compressing between the core 20 and the envelope 21 a cylinder 22 made of some resilient insulating material such as a plasticized resin, an elastomer, etc., the outer diarneter of this cylinder being Aslightly greater than the diameter of the envelope and its inner daimeter less than the diameter of the core. After it has been coated with an adhesive substance, this cylinder 22 is placed over the core 20, from which it protrudes at each end. A pull is exerted on either end of cylinder 22, and, after being coated with an adhesive substance, both the core 20 and the said cylinder 22 are introduced into the envelope 21. After core 20 and cylinder 22 have been introduced, the pull on cylinder 22 is relaxed and the ends of the latter cut so that the end plates 23 which are tightened by the nuts 24 screwed onto -the fittings 25 can apply suitable compression force onto said ends of cylinder 22.

Clearly, instead of reducing the thickness of cylinder 22 by exerting a pull on its ends, the cylinder may be introduced or formed at a temperature below utilization temperature, the subsequent expansion resulting from the rise in temperature being taken advantage of to set the cylinder under compression.

Furthermore, instead of using a one-piece cylinder, the filling can be achieved by the use of stacked resilient annuli compressed together when the end plates are tightened.

It is to be clearly understood that our invention is by no means limited to the embodiments described hereinabove and that, in particular, the shape and materials used for the core and the envelope can be modified as can also the attachment fittings, regardless of whether they are associated with the core, with the plates or with the envelope itself. Moreover, the material used for the filler elements can likewise be modified provided it satisfies the insulation and adhesiveness requirements.

What is claimed is:

1. An insulator comprising an elongated insulating core resistant to traction, a metal fitting connected t0 each end of said core, a hollow insulating envelope enclosing said core and defining an annular space between said core and said envelope, a plurality of spaced rings dsposedjn, said, annular. .space saiclrings being -madeeo insulating material and being fully bound to the envelope and to the core.

2. An insulator as dened in claim 1, wherein the rings have a respective internal and external flange adhering to the respective core and envelope by means of a polymerized resin.

3. An insulator comprising an elongated insulating core resistant to traction, a'metal fitting connected to each end of said core, a hollow insulating "envelope en-` closing-said-core andfdening `anannular space between'A said core and said envelope, anel'apluralityof` adjacent-r iilling -annular --layers and separating rings' disposed' alternately within said annular spaceysaid lling-annularlayersi being made ofa solid'insulating-1nedium-and'fsaidseparating rings being made oan elastic insulating substance;

adhering Yclosely to saidfcore and toisaid j envelope;

4Q Anvinsulator asV dened in-clainr` 3, w-hereine--saiclJ ringsammade of.elasto,mer of. thetype ,comprising a,resin..

produced by the reaction of alkaline polysuldes with a hydrocarbon and said elastomer adheres closely t0 said core and to Asaid envelope.

References Cited in the le of this patent UNITED STATES PATENTS Hennef-4.,---144444--4-.4- June 291119,59 

1. AN INSULATOR COMPRISING AN ELONGATED INSULATING CORE RESISTANT TO TRACTION, A METAL FITTING CONNECTED TO EACH END OF SAID CORE, A HOLLOW INSULATING ENVELOPE ENCLOSING SAID CORE AND DEFINING AN ANNULAR SPACE BETWEEN SAID CORE AND SAID ENVELOPE, A PLURALITY OF SPACED RINGS DISPOSED IN SAID ANNULAR SPACE, SAID RINGS BEING MADE OF INSULATING MATERIAL AND BEING FULLY BOUND TO THE ENVELOPE AND TO THE CORE. 